Normally, a human's voice sounds different between when directly hearing own voices and when hearing a recording of the own voices, and a feeling of strangeness occurs. This is because voices through bone conduction is heard in addition to voices through air conduction when own voices are heard.
In order to eliminate such feeling of strangeness during playback, for example, Patent Literature 1 discloses a singing voice recording karaoke system that converts raw singing voice recording data on the basis of frequency conversion data of any user when the any user sings a desired song. The frequency conversion data is frequency conversion data for converting voices only through air conduction into combined voices in which voices through bone conduction are added to the voices only through air conduction, the combined voices being acquired on the basis of frequency characteristics of the respective voices input from an air conduction microphone and a bone conduction microphone simultaneously with regard to any user.